Digital printing refers to methods of printing from a digital based image directly to a variety of media. It usually refers to professional printing where small run jobs from desktop publishing and other digital sources are printed using large format and/or high volume laser or inkjet printers. Digital printing has a higher cost per page than more traditional offset printing methods but there is generally a cost saving in preparing for printing in terms of time and materials.
Digital printing also allows for on demand printing, short turn around, and modification of the image with each impression.
There are a number of printers that print onto precut media of final desired size. Office desk top printers which generally accept A4 sheets are examples of this. With such small sheets of media, the image is generally fairly well aligned with the edges of medium.
Wide format printers are required for printing wide products, such as signs and posters, for example. A wide format printer can, however, also be used for printing smaller artwork such as posters and the like.
Wide format printers accept large media, as roll stock or sheets, and may be configured to print a number of print jobs on the media across its width and on part of the roll.
After printing, the media is sectioned to separate the individual printed areas, which may be different artwork for possibly different projects, perhaps even for different clients.
A number of similar or different pieces of artwork, that may be part of the same or different print jobs, possibly for different clients, may be arranged across the width of the media to minimize media wastage. After printing, the printed section of the media may be cut off the remaining roll of media, and the individual pieces of artwork may be cut to size.
In digital printing, the images are not necessarily aligned with the edges of the medium. This is particularly the case with wide format and super wide format printing and where the medium is flexible and large.
To section the medium, cutters must therefore be carefully aligned with respect to the artwork itself or with registration marks. This has traditionally been achieved manually after removing the print job from the printing machine.
The vast majority of applications for printed matter on flexible media such as paper are rectangular. To separate from the media, after printing, cuts are required parallel and perpendicular to the printed artwork. Registration marks are often printed together with the image of interest, and then on a separate machine or simple cutting table, cutters, such as scissors, knives or guillotine blades, cut the media using the registration marks for alignment purposes.
The cutting may be positioned to follow the edge of the printed area, along the edge, or a margin may be left, or the cutting may be configured to follow the edge within the edge, to remove the outermost, known as the bleed.
In all cases, whether the edge of the image is used for registration or separate registration marks are printed, careful alignment is required to ensure that the media is cut properly.
Typically, a simple cutting table is used for cutting. The printed media is removed from the printing machine and taken to the cutting table and then the cutters are aligned using registration marks or the edge of the printed area, either manually or automatically. Alignment of cutters with the images, even where registration marks are used for so doing, is time-consuming, reduces throughput and increases the total system cost. Even in the case of a digital cutter attached to the printer, such a cutter operates only according to registration marks and manual adjustment by the user and there is no automation and control by the printer itself based on the actual data printed.
Manual cutting is subject to a high level of human error, resulting in wastage.
With small objects, such as book pages that are A4 or A5, but even larger objects that are up to and including, say A2 or A1 size pages, a small deviation is not noticeable. When printing across the width of a wide format printer having a width of 1 to 5 meters, a very small angular misalignment becomes magnified as one moves across the media.
U.S. Pat. No. 6,874,418 to Ullrich et al. titled “Cutting device for cutting a printing material in the printing unit of a printing device” describes an electrographic printing devices, for printing media such as paper webs, which addresses the problem of a malfunction requiring that the printing material has to be removed from the printing unit the drive rollers for the printing material becoming dirtied by non-fixed toner images. A cutting device is provided that presents a reel cutter that is guided in a guide groove of a guide tube. When a malfunction occurs, the cutting device is activated, the reel cutter cuts the printing material, and the cut sections of the printing material are pulled out of the printing unit separately. Thus U.S. Pat. No. 6,874,418 to Ullrich et al describes a cutter on a track coupled to the same chassis as the track of the print head, that is designed for separating a jammed medium. It will be appreciated that the medium will invariably be tugged erratically from the print table and the cuts will not be in parallel to the printing. Furthermore, the cutter may even be upstream of the printing. It will therefore be appreciated that Ullrich does not provide or anticipate a solution to the problem of aligning cutters with printed images.